The Donaldson on the left was run 6800 km (4200 miles) with a group II 10w30, CI-4/SL. He has run that brand/type oil for over 100,000 km. The one on the right was run 3300 km (2050 miles) with a group I 15w40 that claims CH-4.
The bypass valve on the bad one was not stuck, and actually felt weak. Obviously as mentioned, poorer maintenance all around. Cheap oil, cheap filter, cheap owner.